Pattern matching using regex in Python

Question

I'm trying out a strong password detection task that uses regular expressions to make sure the password string it is passed is strong. A strong password is defined as one that is at least eight characters long, contains both uppercase and lowercase characters, and has at least one digit. We need to test the string against multiple regex patterns to validate its strength.

Here's my proposed code for the same:

import re
def password_detect(exp):
    if len(exp) >= 8:        
        passRegex = re.compile('r[(a-z)+(A-Z)+(0-9)+]')
        mo = passRegex.search(exp)
        if mo.group() != None:
            print("Password is strong")
        else:
            print("Password is not strong")

    else:
        print("Password length is not strong")

It returns this traceback:

Traceback (most recent call last):

  File "<ipython-input-245-4202435a0efb>", line 1, in <module>
    password_detect('oldG2020')

  File "<ipython-input-243-39585a6ade11>", line 5, in password_detect
    if mo.group() != None:

AttributeError: 'NoneType' object has no attribute 'group'

Which is a NoneType being returned? It seems to follow the rules. Thanks.

@DYZ: oldG2020 as a password should have returned a match as per the given criteria. — srkdb, Aug 21 '18 at 22:54
Do you realize `[(a-z)+(A-Z)+(0-9)+]` matches only one character? `(`, `a`, `-`, `z`, `)`, `+`, `A`, `Z`, `0`, `9`? — emsimpson92, Aug 21 '18 at 22:54
@emsimpson92: That was my fear. I wanted it to match one of each, hence I placed them in separate parentheses. — srkdb, Aug 21 '18 at 22:55
Your regular expression is probably totally incorrect. It demands that a password starts with an `"r"` - is this intentional? — DYZ, Aug 21 '18 at 22:55
@MadPhysicist: mo alone doesn't cut it. It gives password_detect('oldG2020') Password is not strong which is obviously wrong. — srkdb, Aug 21 '18 at 22:56
To add to what DYZ was saying, the "r" goes outside of the pattern like so: `r"[(a-z)+(A-Z)+(0-9)+]"` — emsimpson92, Aug 21 '18 at 22:56
@emsimpson92: Yeah, the r was a bad mistake. Working on the one character issue now. — srkdb, Aug 21 '18 at 22:58
Okay, I got it working with this: r"^(?=.*[\d])(?=.*[A-Z])(?=.*[a-z])" Still a little confused as to why the ^ is used, since I get the idea that it insists the password begin with a number? — srkdb, Aug 21 '18 at 23:14
If you get it working @db18, you can self-answer if nobody else does. — LinkBerest, Aug 21 '18 at 23:22

Pattern matching using regex in Python

0 Answers0